The structural changes taking place in the enzyme thymidine phosphorylase (TPase, also known as PD-ECGF) that are required to achieve catalytic competence upon binding thymidine and phosphate have been simulated by means of targeted molecular dynamics (tMD). The hinge regions were characterized by structural homology comparisons with pyrimidine nucleoside phosphorylase, whose X-ray structure ha...

In the title mol-ecular salt, C(8)H(13)N(2)O(+)·C(7)H(3)N(2)O(7) (-)·H(2)O, the pyrimidinium cation is essentially planar, with a maximum deviation of 0.009 (1) Å. The cation undergoes an enol-keto tautomerism during the crystallization. In the crystal, the ion pairs and water mol-ecules are connected via O-H⋯O, N-H⋯O and C-H⋯O hydrogen bonds, forming two-dimensional networks parallel to the bc...

A GC/MS method suitable to conduct practical toxicological analyses of unspecified opiates including hydrocodone or hydromorphone is presented. Silylation can be a convenient reaction to derivatize unknown analytes in toxicological samples. However, silylation of drugs with tautomeric keto/enol groups in molecular structure can cause analytical problems due to poor reproducibility. After using ...

Curcumin, derived from Curcuma longa plant has been shown to exhibit antioxidant, antiinflammatory, antiviral, antibacterial, antifungal, and anticancer activities and thus has a potential against various malignant diseases, diabetes, allergies, arthritis, Alzheimer’s disease, and other chronic illnesses [1–3]. In the light of these promising propertiesseveral questions need to be answered in o...

The low-lying excited singlet states of the keto, enol, and keto-imine tautomers of cytosine have been investigated employing a combined density functional/multireference configuration interaction (DFT/MRCI) method. Unconstrained geometry optimizations have yielded out-of-plain distorted structures of the pi --> pi and n --> pi excited states of all cytosine forms. For the keto tautomer, the DF...

Proton tautomerism is a general phenomenon in organic molecules and plays a vital role in many fields of chemistry and biochemistry. The tautomerism of salicylideneanilines [eq(1)] has attracted a considerable attention because it is closely related to thermoand photochromism. Salicylideneanilines greatly favor the enol form over the cis-keto form in the gas phase. We demonstrate here that the ...

Schiff-base macrocycles that combine keto-enamine and enol-imine tautomers within the same ring were synthesized and characterized. These new macrocycles form host-guest complexes with organic cations and unexpectedly form a lyotropic liquid crystal in organic solvents such as chloroform and toluene.

The title compound, C21H24O9, crystallizes with two independent mol-ecules in the asymmetric unit which are almost centrosymmetrically related to each other. The ethano-ate group in one of the two mol-ecules is disordered over two positions with a site-occupation factor of 0.880 (7) for the major occupied site. In the crystal, the 1,3-diketone group exists in the keto-enol isomeric form due to ...

The photophysics of methyl salicylate (MS) isomers has been studied using time-dependent density functional theory and large basis sets. First electronic singlet and triplet excited states energies, structure, and vibrational analysis were calculated for the ketoB, enol, and ketoA isomers. It is demonstrated that the photochemical pathway involving excited state intramolecular proton transfer (...